A lot of research is going on now into what gives online writers credibility - how it is earned; how it can be rated numerically, etc. This work is important because it's directly related to the value of the web itself. If I want to hire a plumber, I'll most likely do it by asking a friend for a recommendation. The credibility of my friend with me is so high that I'm probably going to accept his judgment without question. But what if I've just moved to a new city? I can go to Google and search for Boulder, Colorado Plumbers and probably find someone, but it's not nearly as likely to be someone I'm happy with on the first try. (And of course, the credibility that Google has with me is even more than I would have for something like http://www.servicemagic.com/, even though that actually might be just as good.)
But the credibility problem has been around for decades. Take a look at Usenet (or, for all practical purposes nowadays, Google Groups.) When I was spending a vast amount of time reading and posting there, back in the late 80's and early 90's, you could spend a few hours reading a few month's posts in a group like rec.sport.billiards and get a pretty good idea who was worth reading and who was not. It had to do with authority, knowledge, politeness, willingness to respond to newbie posts, things like that. You can still do it today, sometimes - it won't take much reading in comp.lang.c++.moderated before you see that James Kanze is someone to whom it is well worth paying a lot of attention.
Of course, it worked in the other direction too. There were individuals who gained notoriety rather than credibility, and you would tend to pay less attention to these individuals than the average poster whose name you didn't even recognize.
The other interesting thing to notice is that if you ever met a person in real life, his credibility would soar with you. So if you watched an online argument between someone you had met and someone you had not, you would almost always tend to side with the one you had met.
What made me think about all this was the flack about Internet Explorer 7 and the Google Toolbar, as reported by Scoble. The actors in the drama gained and lost credibility in my sight off and on as I followed along. Since I haven't ever met them, my estimation of their credibility was based solely on their online messages. For example, when the Register posted its first correction, it said that Scoble himself had actually seen the bug. I hadn't gotten that impression from the online reports, and Robert later denied it himself. So where did the report come from? A misunderstood phone message, a private email? Don't know, don't care. It's not verifiable from public statements. The Register credibility drops.
A message is posted in the Scobleizer comments, claiming to have replicated the bug. Robert asks for screen shots. None are made available publically, but later many commenters sneer at the fact that "The bug was reported on your own comments!" Well, the original poster never responded again that I saw, so their credibility, along with the other posters, drops. A commenter named Andrew makes some snotty comments, including name-calling. His credibility drops a lot. Scoble handles him perfectly, choosing to ignore the first insult and calling him out on the second. Good responses, and more cred for the Scobleizer.
So, based strictly on what I saw online, it's clear to me that Robert is the most credible actor in this drama, and I tend to buy the Microsoft side of the story. Of course, I don't know any of the private details, and I'm not likely ever to. But the only way the Register could recover their cred with me would be to call me up personally and tell me exactly what really happened. I'm not holding my breath.